Hi Axhash! Your gestures look so wonderful! It shows you have a lot of understanding behind your loose sketches. Your strokes feel definitive, confident, and fluid! I'd love to see you develop on them, and maybe make a more polished piece based on some of these.
There's a website called posemaniacs that has a tool with 3D models to draw from. The page that specifically is labeled "Hand Viewer" has the models in strictly grayscale, that acts as though there's a light shining directly from the viewer's eye, or just straight ahead. So the "closer" the object is to the screen the brighter it is.
http://www.posemaniacs.com/tools/handviewer/ It might give you some simple perspective on shadow's workings. there are plenty of free resources on the subject online. Here's one small example, but it might give you a good starting point to experiment with.
http://www.deviantart.com/art/Shading-Tutorial-A-98851485
